Telephone system



June 10, 1930. c. D. KOECHLING ET AL 1,763,161

'TELEPHONE SYSTEM Filed Nov. 1, 1928 CHARLES L7. KOEGHL/NB WVENTORS GERALD l/ huve Patented June 10, 1930 UNITED STATES PATENT OFFIcE cnARLEs n. KOECHLING, or BROOKLYN, AND GERALD v. KING, OF JAMAICA, Raw YORK, ASSIGNORS TO BELL TELEPHONE LARoRAToRrns, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION on NEW YORK TELEPHONE sYsTnM Application filed November 1, 1928. 'SerialNo. 316,433.

This invention relates to telephone sys tems, and particularly to automatic private branch exchange systems.

The object of this invention is to economically arrange a system of this type for conference call connections.

Heretofore systems have been used in which conference call connections were established by having the subscriber dial a certain number, thereby causinghis line to be automatically connected through line finders and selective switches with all of the other subscribers lines arranged for confer-- ence connection. A system of this general 5 type is disclosed in the Patent 1,264,158 of April 30, 1918, to H. P. Clausen. In that system ringing current and talking current are supplied by means individual to the line circuits of the called lines.

According to a feature of this invention, each subscribers line terminates in an autoniatic selective switch. These switches are so arranged that when a conference connection is desired the calling subscriber by dialing a certain number causes his individual switch to connect his line with all of the other subscribers lines arranged for conferonce connection. The ringing current and talking current are supplied to the called subscribers lines from the circuit arrangement of the automatic switches individually associated with these called subscribers lines and not from means individual to line circuits of the called subscribers lines as in the prior art. V

Another feature of the invention is the provision of means whereby when a conference connection is made, any prev1ouslinetO-line connections to any of the called subscriberslines included in the conference connection are disabled. Another feature of the invention is the provision of means whereby, if a line-toline connection is established, ringing current is applied to the called subscribers line from the automatic switch associated with said called subscribers line, while talking current is supplied to the connec ion from Y the switch individual to the calling sub-' scribers line.

Another feature of the invention is the provision of means whereby, if a line-to-line accompanying drawings in which Fig. 1

shows in diagrammatic form interconnections between three subscribers lines to illustrate the system in a general manner, and Fig. 2 shows a connector switch and associated circuits of a single subscribers line.

Referring now to Fig.1, 1, 2 and 3 indicate subscribers lines, 4, 5 and 6 indicate connector switches individual to said lines and the boxes 7, 8 and 9 indicate the circuits associated with said connectors, respectively. The connectors are shown having access to terminal banks in which the first set of terminals in the bank of switch 4 is multipled and associated with the circuits 8 and 9 of switches 5 and 6 for a conference call connection, while'theother sets of terminals of the banks of all three switches are multipled together, each set leading to a separate subscribers line through the circuits associated with said subscribers individualconnector. An ordinaryline-to-line call from subscriber of line 1, to, forexample, the subscriber of line 3, will be established by having the subscriber of line 1 dial the number of line 3 and thereby actuate the associated connector and its circuit 7 to cause aconnection to be extended through the fourth set of terminals and circuit 9 to line .3. Similarly,,- calls from other subscribers in line-to-line calls will be extended in a simi lar manner. subscriber 1' has been arranged for confer ence calls with subscribers 2 and 3. In case a conference connection is desired, the subscriber of line 1 will dial a special code to actuate switch 4 and circuit 7 to establish a connection with the first set of terminals which, as noted, is connectedin multiple to circuits-8 and 9 and these circuits are actu In this circuit only the line of' ated to establish connections to the corresponding subscribers of lines 2 and 3.

Detail descriptions will now be made of lineto-line call followed by a conference Gilli in connection with the circuit shown in Fig. 2. It should be understood that this circuit identical for the connectors of all the lines except as described in connection with Fig. 1.. If the connector that of any other line but the line 1, the first set of terminals of the banks of these connectors will be made artificially busy, that is, a ground connection will be made on the sleeve of these sets of terminals, while the first set of terminals of switch 4 which are the conference call terminals will not be connected in. multiple to the connector circuit of line 1. The connector switches are of the standard Strowger step-by-step type well known in the art.

Referring now to Fig. 2 when a calling subscriber removes his receiver from the hook, a circuit is closed for the operation of relay 12 from battery, through the lower winding of this relay, lower outer armatures and back contacts of relays 13 and 1%, through the subscribers loop, upper outer armatures and back contacts of relays 14: and 13, through the upper winding of relay 12, to ground. Relay 12 in operating causes theoperation of relay 15 over a circuit from battery, through the winding of this relay, upper inner armature and back contact of relay 13, upper armature and front contact of relay 12, to ground. Relay 15 in operating prepares a pulsing circuit for the vertical magnet 16 at its upper armature and front contact, establishes a ground connection through its lower inner armature and front contact for the sleeve brush 1?, the purpose of which will be apparent hereinafter, and connects a busy ground to the sleeve conductor 25 to make this line busy to other subscribers.

The circuits are now in condition for the reception of dialing impulses from the calling subscriber. Relay 12 is now released and operated in accordance with the impulses and operates the vertical magnet accordingly over a circuit as follows: Battery,

vertical magnet 16, winding of relay 18, through vertical 01f normal contacts 20, upper armature and front contact of relay 15, and upper armature and back contact of relay 12, to ground. The vertical magnet steps the brushes of this connector to the level in which the terminals of the desired line are located. Relay 18 is operated in this circuit on the first closure thereof and as this relay as well as relay 15 have slow releasin characteristics they are held up during the dialingperi-od. On the first operation of the connector the vertical off normal contacts 20 are operated and the pulsing circuit is thereby transferred through the armature and front contact of relay 18 and operated contacts of the vertical off normal contacts 20. Vdhen the first digit impulses from the calling subscriber cease, relay 18 is released and transfers the pulsing circuit through its armature and back contact to the rotary magnet 19. On the next digit impulses from the calling subscriber, relay12 in releasing for the first time causes the operation of the rotary magnet 19 and the relay 21 over a circuit from battery, through the winding of the rotary magnet 19, lower armature and back contact of relay 22, lower outer arma ture and back contact of relay 23, winding of relay 21, armature and back contact of relay 18, operated contacts of the vertical oil normal contacts 20, upper armature and front contact of relay 15, and upper armature and back contactof relay 12 to ground. Relay 21 is also slow in releasing so that it will be held up during dialing. The rotary magnet 19 in following the succeeding impulses causes the brushes of the connector to be rotated in the selected level until they are connectedwith the terminals of the desired line. Relay 21 in operating prepares a busy test circuit for the line by the operation of its upper armature. This busy test circuit extends through the winding of relay 22 to battery. Relay 21 also extends through its lower armature and front contact, the pulsing circuit hereinbefore traced through the lower armature and back contact of relay 22. This transfer of the pulsing circuit is for the purpose of preventing it from being opened in case relay 22 should operate while the sleeve brush 1? passes over the terminals of busy lines while it is being advanced to the wanted subscribers line.

On the completion of the dialing of the second digit, the re ay 21 remains operated for a short interval after the brushes have made contact with the terminals of the desired line. During this time a busy test is made by relay If the line is idle, relay 22 is not operated and on the release of relay 21 relay will energize over a circuitfrom battery, through the winding of the relay corresponding to relay 13 of the connector of the selected line, upper inner-armature and back contact of the relay 'correspoi'uling to relay 2a, lov. armature and back contact of the relay corresponding to relay 15, to the sleeve terminal of the selective line over the lead correspondin to lead 25, brush 1?, upper armature and back contact of relay 21, upper winding of relay 23, upper outer armature and back contact of relay 22, inner lower armature and front contact of relay 15, to ground. Relay 23 operates sufliciently to close a connection from battery through its lower winding and lower inner armature and front contact to ground at the lower outer armature and front contact of relay 15. Relay 23 is thereby fully actuated to ice tit

lay 13 in the connector of the selected line,

over the circuit hereinbefore trace-d. This ground connection also serves as a busy indication on the sleeve terminal of the selected line. i

If the selected line should be busy the ground on the sleeve terminal would cause the operation of relay 22 from battery, through the winding of this relay, upper armature and front contact of relay 21, before relay is released and immediately after the last rotary impulse has been received, as hereinbefore described, through brush 17 to ground. When relay 21 releases, relay 22 is locked through the make-before-break contact of re lay 21, the upper outer armature and front contact of relay 22, to ground at the inner lower armatureand front contact of relay 15. Relay 22 in operating transmits a busy tone from the tone source 27 through its upper innor armature and front contactof relay 22, the upper outer armatures and back contacts of relays l3 and 14, over the tip conductor of the calling subscribers line, to notify him that the desired lineis busy. 1

As hereinbefore stated if the desired line'is idle the relay corresponding to relay 13 of the connector of this lineis operated on the operation of relay 23. This relay in operating causes the relay corresponding to relay 12 to be disconnected from the line at the upper and lower outer arinatures and back contacts of this relay, prepares a circuit for the relay corresponding to relay 30, and connects ringing currentfrom a common continuous ringing current source 31, for calling the desired subscriber. The circuit for the ringing cur rent may be traced as follows; fronisource 31 through the upper outer armature and back contactof the'relay corresponding to relay 30, upper winding of the relay corresponding to relay l4, outer lower armature and front contact of the relay corresponding torelay 13, lower outer armature and back contact of the relay corresponding to relay 14, to the ring conductor of the desired line, back through the tip conductor and upper outer armature and back contact of the relay corresponding to relay 14, upper outer armature and front contact of the relay corresponding to relay 13, through the inner upper armature and back contact of the relay corresponding to re lay 30, to ground. A condenser corresponding to condenser 32 andcircuits associated therewith are provided to permit the ringing of the 'desiredsubscriber to be heard by the calling subscriber, the circuit connection being extended from the inner lower armature of the relay corresponding to relay 14 to the ringconductor of the pair 36, the associated ring terminal and brushes and ring conductor of the calling subscribers switch. A common machine ringing source 34 is provided which supplies intermittent ringing current to the called subscribers line at the next silent period of ringing fromthis sourcein place of the continuous ringing from source 31. The

common relay 35 is released during this period and completes a circuit for the operation of the relay corresponding to relay 30, over a circuit as follows: Froinbat-tery, through the winding of this relay, inner lower armature and front contact of the relay corresponding to relay 13, resistance corresponding to resistance 38, lower make-beforebreak contacts of. the relay corresponding to relay 30, armature and back contact of relay 35, to ground. Therelay corresponding to relay isthereby operated partially to close the connection through its lower inner armature and front contact so that when relay 18 again operated, a c1rcu1t is completed for this relay from ground through the top armature and front contactof relay 35, through the inner lower make-before break contacts and lower inner armature and front contact of the relay corresponding to relay 30, to short circuit the resistance corresponding to the resistance 38 and thus cause the relay corresponding to relay 30 to complete its operation. The connection is thereby transferred from theringing source 31 to the machine ringing source 34, through the upper arma tures and front contacts of this relay and a locking circuit is provided for itself through the middle lower armature and front contact, to ground, under control of the relay corre sponding to relay 13.

'ld hen the called subscriber answers, the relay corresponding to relay 14 is operated through its upper winding suiiiciently'to close a circuit from battery, through its lower winding, lower'iniddle armature and front contactof the relay corresponding to relay 13, its upper inner armature and front contact to ground to fully operate it. This relay in operating breaks the ringing current connection, disconnects the condenser corresponding to condenser 32, and closes the talking circuit from the leads corresponding to loads 36, through the upper and lower out-era, arinatures and back contacts of the relay corresponding to relay 24, and the upper and lower outer arinatures and front contacts of the relay co responding to relay l4, to the called subscribers line completed tothe called subscriber and talking battery is supplied to the called subscribers line through the windings of relay 37, where as the talking battery for the calling subscriber is supplied through the windings of The connection is now relay 12 over a circuit as hereinbefore described. The circuit for the talking battery for the called subscriber may be traced as follows: From battery, through the lower winding of relay 37, lower middle armature and back contact of relay 24, ring brush of the connector of the calling line, through the ring conductor of the pair of conductors corresponding to pair 36, lower outer armature and back contact of the relay corresponding to relay 24 of the called subscribers connector, and the lower armature and front contact of relay 14 of this connector, through the called subscribers loop, the upper outer armature and front contact of the relay corresponding to relay 14, the upper outer armature and back contact of the relay corresponding to relay 24, tip conductor of the pair corresponding to pair 36, tip brush of the connector of the calling subscriber, upper outer armature and front contact of relay 23, fourth upper armature and back contact of relay 24, upper winding of relay 87, to ground. Relay 37 operates in this circuit but performs no useful function at this time. The calling subscribers line is connccted through the condensers 39 and 40 t0 the called subscribers line for talking purposes.

When the calling subscriber replaces the receiver on the hook at the end of the conversation, relay 12 is released, causing the release of relay 15. This relay in turn causes the release of relay 23 thereoy closing the circuit for the release magnet 41 from battery, through the winding of this magnet, operated contacts of the vertical off iornial contacts 20, upper middle armature and back contact of relay 23, third upper armature and bacl; Contact of relay 24, upper armatures and back contacts of relays 15 and 12, to ground. The connector is now returned to normal and on the release of the vertical oil normal contacts 20 the circuit for the release magnet is opened. On the release of relay 3 the release of the relays in the connector circuit of the called subscribers line corresponding to relays 13, 14 and 30 is effected and thus this circuit is also restored to normal condition.

ll hcn a conference connection is desired a certain code number is dialed by the calling subscriber which causes his connector to select the conference number in the same manner as any other line is selected as hereinbefore described. The conference line is multiplcd to the subscribers lines that are included in the conference connections and terminates in the connectors of said lines at the point 42. \Vhen these lines are called all relays 43 are operated over the sleeve circuit instead of the relay 13 as in an ordinary call.

Reference will now be made to the connection through one of the connectors, bearing in mind that the functions are the same for all of the connections included in the conference connection. The circuit for relay 43 through the call originating connector originates at the front contact and inner upper armature of relay 23. Relay 43 closes an obvious circui-t for the operation of relay 24. Relay 24 closes a circuit for the operation of relay 3'? as follows: Battery, lower winding of this relay, inner lower armature and front contact of relay 24, upper inner armature and back contact of relay 14 to ground. Relay 37 provides a locking circuit for itself from battery, lower winding of this relay,lower inner armature and front contact of relay 24, lower armature and front contact of relay 3'? to maintain it operated after relay 14 is later operated as will hereinafter be described. The operation of relays 24 and 37 causes the operation of relay 13 from battery to the winding of this relay, upper inner armature and front contact of relay 24 and upper arn'iature and front contact of relay 37, to ground. From this point on the operations of the connector is the same for station to station calls, except that the conference line is connected to the stations from point 42 through operated contacts of the relay 24 and that the ringing of the individual subscriber in the conference connection is not heard by the calling subscriber. It should be noted that the 0011- denser 32 is not included in the conference connection but only to the ring conductor for ordinary calls to subscribers.

The talking battery for the called lines is furnished by the relays 12 associated with the individual connectors of these lines. The circuit from the talking battery for a called line may be traced from battery, through the lowerwinding of relay 12, lower outer armatures and front contacts of relays 24 and 14, through the subscribers loop, upper outer armatures and front contacts of relays 14 and 24, upper winding of relay 12 to ground. It should be noted that in this case the talking battery for the calling line is furnished as in station to station calls through the relay 12 of the connector associated. with this line. It should also be observed that a retardation coil 44 is bridged across the tip and ring conductors of conference line 42. This is for the purpose of providing a path for the battery and ground connection through the windings of relay 87 and the brushes of the connector of the calling line, in order to insure a good electrical contact between these brushes and the conference line terminals. This battery and ground are not serving as a talking battery in this connection.

If a line in the conference connection group is busy in a connection in which it is a calling line, when a conference call is originated, the operation of relay 24 of the connector of this line will connect the conference line to the station and will release relay 37 and then reop'erate it by a circuit closed from battery through its lower winding to grount at the upper inner armature and ba'clrcontact ofreand front contact of relay 24. The normal release circuit is not closed at this time as relay 12 will be operated due to the called subscriber being engaged. Theconnection of the corn ference line with this station will then function in the manner hereinbefore described in connection with an idle line, except that relay 14 will operate immediately without transmitting ringing current to the called subscriber if the receiver of this subscriber is off the hook. The operation. of relay 14 takes place in the manner hereinbefore described in connection with a line to line call when the called subscriber removed his receiver from the hook. If the receiver of this subscriber is on the hook his line is called in the usual. manner for line to line calls.

If a line in the conference group is busy ina connection in which it is a called line, when a conference call is originated, the operation of relay 24 of the connector of this line will release relay 13 of this connector and connect the conference line to the station. The release of relay 13 will in turncause the release of relays 30 and 14 of this connector. The release of relay 14- causes the operation of relay 37 and this relay in turn causes the reoperation of relay 13. If the receiver of the called subscribers station is off the hook relay 14 will immediately reoperate. If the receiver of the called subscriber is on the hook ringing current will be connected to this station in the usual manner. Resistances 46 in tip and ring conductors of the conference line 42 are provided so that in case the line of any subscriber in the conference group should be crossed or grounded the conference group arrangement will still be operative in connection with the other stations in the group.

Although this invention has only been shown in connection with one circuit arrangement it should be understood that it could readily be applied to a number of other systems without departing from the spirit of the invention and that it should only be limited by the scope of the appended claims.

What is claimed is:

1. In a telephone system, lines, an automatic selecting switch for each line, means responsive to the actuation of the switch of any one of said lines for associating said line with all of the other lines, and means associated with the switch of each of said. called lines for individually applying ringing current and talking current to the correspond ing called lines.

2. In a telephone system, lines, an automatic switch associated with each line, means responsive to the actuation of the switch of any one line for connecting said line to all of the other lines, means responsive to the establishing of such a connection and associated with the switches of said connected lines respectively for applying ringing current to said lines individually, and means effective on the establishment of a connection tosaid lines respectively and associated with the switch of these lines respectively for removing the ringing current and supplying tallring current to said lines individually.

3. In a telephone system, lines, an automatic switch associated with each line, a trunk, means for selecting said trunk in re sponse to the actuation of the automatic switch of any one line, means individual to the other lines responsive to the selection of said trunk for applying ringing current to said lines respectively, meansrendered effective by the seizure of said other lines for removing said ringing current from said lines individually and for applying talking current to said lines individually and for connecting the trunk to said lines.

4. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of saic lines for establishing a line-to-line connection, and means responsive to the actuation of the connector of any one of said lines for connecting said line toall of the other lines and for disabling any previous line-to-line connection to any of said other lines. 7 V

5. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of said lines for establishing a line-to-line connection, means responsive to the actuation of the connector of any one of said lines for connecting said line to all of the other lines, and means for disabling any previous line-to-line connections, the means for disabling a line in this respect, whether a calling or a called subscribers line, being individual to the connection of the line thus disabled.

6. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of said lines for establishing a line-to-line connection and for establishing a conference connection between all of said lines, and means responsive to the establishing of a conference connection for disabling any previous line-toline connections;

7. In" a telephone system, lines, an automatic selecting switch for each line, means responsive to the actuation of the switch of any one of said lines for connecting said line with any other desired line, and means responsive to such a connection for applying ringing current to the called line from. the switch individual to said line and for supplying talking current to the connection from the switch individual to the calling line.

8. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of said lines for establishing a line-to-line connection and for establishing a conference connection betw on all of said lines, means associated with each connector operative in case of a line-to-line connection to apply talking current for the connection from the means associated with the connector of the calling subscribefis line and to apply ringing current from the means associated with the connector of the called eubscribers line and operative in case of a conference connection to apply both talking and ringing current to the called subscribers individually from the means associated with the connectors of the called subscribers lines, respectively.

9. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of said lines for establishing a linc-to-line connection and for establishing a conference connection between all of said lines, means associated with each connector operatire in case of a line-to-line connection to apply talking current for the connection from, the means associated with the connector of the calling subscribers line and to apply ringing current from the means associated with the connector of the called subscribers line and operative in case of a conference con nection to apply both talking and ringing current to the called subscribers individually from the means associated with the connectors of the called subscribers lines, respectively, and to apply talking current to the calling subscribers line from the means associated with the connector individualto said calling line.

10. In a telephone system, lines, an automatic selecting switch for each line, means responsive to the actuation of? the switch of any one of said lines for establishing a lineto-line connection, means responsive to the actuation of the switch of any one of said lines for establishing a conference connection to all of the other lines, and means re sponsive to the establishing of a line-to-line connection for transmitting an audible signal to the calling line and means responsire to the establishing of a conference connection for omitting such signal to the calling line. i

11. In a telephone system, groups of lines, a connector switch for each line, means responsive to the actuation of the connectors of any of said lines for establishing line-to-line connections and means responsive to the ac tuation of any one of the connectors of certain of said lines for connecting the asso ciated line with all of the lines simultane ously in any one of said groups.

12. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of said lines for establishing li'ne-to-line connections, and means responsive to the actuation of the connectors of certain of said lines for establishing conference connections between certain of said lines and for disabling any previous line-to-line connections between any of said certain lines.

13. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any of said lines for establishing line-to-line connections, means responsive to the actuation of the connector of one of said lines for establishing a conference connection to certain of said lines, means responsive to the actuation of the connector of another line for establishing a conference connection to certain of said lines, and means responsive to the establishing of acontcrence connection for disabling any previous lineto-line connection to any of the lines involved in said conference connection.

14:. In a telephone system, lines, a connector switch for each line, means responsive to the actuation of the connector of any one of: said lines for establishing a line to line connection and for establishing a conference connection between all of said lines, and means responsive to the establishing of a conference connection for disabling any previous line to line connection in which the calling subscriber has abandoned the connection by replacing his receiver on the switc'hhool-r.

In witness whereof, we hereunto subscribe our names this 31st day of October 1928.

CHARLES D. KOEUHLING. GERALD V. KING. 

